JPS6044135B2 - How to manufacture pneumatic tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a pneumatic tire that can produce a uniform pneumatic tire suitable for high-speed driving with a high degree of probability and does not require pass/fail screening using an inspection machine.

Recently, roads have been improved and cars are being used at high speeds.

In particular, there is a demand for tires with excellent ride comfort, balance, and uniformity. In order to meet this demand, we must accurately produce green tires, accurately load them into vulcanization molds, and perform vulcanization molding. Furthermore, we must ensure the uniformity of the vulcanized tires. It is necessary to check the suitability for use at high speeds. That is, it is important that the mass distribution be symmetrical with respect to the tire's equatorial plane or rotational axis as an axis of symmetry, and that centrifugal force act uniformly when the tire rotates.

In particular, the position of the tread rubber, which accounts for more than half of the tire's weight and is located at the outermost part of the tire, is a major factor in determining the uniformity of the action of centrifugal force. If the action of centrifugal force is uneven, abnormal vibrations occur during use, resulting in a tire with poor riding comfort. Therefore, conventionally, in order to align the center of the tread strip with the center of the car gas, a tread strip is made using a base with a notch in the center of the width, so that a small protrusion is formed at the center of the crown width of the tread strip. The method used was to extrude the tread strip and irradiate it onto the car gas on the molding machine, aligning the center protrusion of the tread strip with a beam that indicates the center of the width of the car gas, and then overlaying the strip on the rotating car gas. .

However, it is difficult to overlap the protrusions in a rotating state, and if the protrusions are wide, the accuracy of centering will be poor, and if the protrusions are made too wide, they will collapse during transportation. Since the front and rear parts of the tread strip are thin and the tread strip is black, it is difficult to identify the protrusions of the moving tread strip under the lighting inside the factory building, making it difficult to accurately mark the protrusions on the beam. I couldn't match it.

Furthermore, in order to firmly adhere the tread strip to the carcass, the tread strip on the carcass is strongly pressed down with a stitcher roll, so the protrusions collapse and there is no indicator indicating the center of the green tire, which is removed during the next vulcanization process. During the process, when loading the vulcanization mold into a vertically divided vulcanization mold, it was not possible to load it into the correct position. Therefore, all vulcanized and molded tires are inspected using a tire uniformity inspection machine, and only tires with good uniformity are used after rejecting the tires. As described above, there was a problem in that the manufacturing cost was high due to the number of inspection steps and rejected products.

Therefore, the inventors have searched for a method to solve these problems.

In other words, a small groove (with a width of 0.5
Extrude a tread strip with a groove shallower than 2 Twt in depth, fill the small groove with a conspicuous color comb paint that is different from the color of the tread rubber, and add a color center line (
A width of 0.5 to 2 mm) is applied, and the center position of the tread strip is aligned and overlapped with the center position of the width of the carcass formed on the tire molding machine, with the center position of the color center line 4 as a reference. A green tire is formed, and the color center line is aligned with the center position of the upper and lower symmetrical planes of the mold.

Usually, the upper and lower dividing planes of the mold are formed at the center of the upper and lower symmetrical planes of the mold. Therefore, the trend color center line of this raw tire is placed relative to the center dividing plane of the vulcanization mold divided into upper and lower parts, that is, the center position that is the symmetrical plane of the upper and lower parts of the mold. When loaded and vulcanized, parter is formed on the split surface of the vulcanization mold in the center of the trend surface. An inline (protruding line) is formed.

Therefore, if the relative positioning is accurate, the color center line will coincide with the parting line and the color center line state will be lost. Therefore, we have devised a method for manufacturing a pneumatic tire that makes it possible to determine the uniformity of the tire by comparing the distance between the parting line and the color center line. The width of the small groove is preferably in the range of 0.5 to 2 wn; if it is narrower than this, the paint transfer disk will not rotate smoothly, and if it is 2 wn or more, the center pointing accuracy will deteriorate.

In addition, the width of the color center line is determined by the thickness of the transfer disk rotating in the small groove, and the width is 0.5 to 2Tf0It.
The range is preferably within the range of 0.5W0fL, and if it is narrower than 0.5W0fL, the paint will not be clearly drawn on the tread strip. Next, aspects of the present invention will be specifically described in detail based on drawings showing an example of implementation.

Fig. 1 is a partial perspective view of the main part showing the process of forming a color center line on a tread strip, and Fig. 2 shows a green tire formed with a tread strip having a color center line. Fig. 3 is a partial perspective view of the main part showing an axial cross section (carcass ply illustration omitted), and Fig. 3 is a front view showing the outline immediately after taking out from the vulcanization mold (trend pattern etc. omitted), with color center When the line exactly overlaps with the center dividing plane of the mold, it becomes a parting line 15, the color line almost disappears, and the state of the color center line is lost.

In Fig. 1, 1 is a tread strip, 2'' is a crown part, 3 is a small groove provided at the center of the width of the crown part, 4 is a color center line in which colored rubber paint is applied to the small groove 3;
5 is a mouthpiece of the extruder, 6 is a protrusion of the mouthpiece 5 that forms the small groove 3, 7 is a paint tank, 8 and 9 are pickup rolls,
10 is a disk for transferring color center lines.

In the step of forming the color center line on the tread strip 1, first, when the tread strip 1 is pushed onto the conveyor belt through the mouthpiece 5 having an approximately trapezoidal opening, the opening of the mouthpiece 5 is pushed out onto the conveyor belt. A small groove is formed at the center position of the width of the crown portion 2 by the protrusion 6 provided at the center of the width of the crown portion 2.

In this example, the protrusion 6 forms a small groove 3 having a semicircular cross section with a radius of 0.7 Tf$t. Next, to form the color center line 4, a conspicuously colored rubber paint, in this example, white paint, is poured into the paint tank 7, and the paint is passed through pickup rolls 8 and 9 to a thickness of 1w in this example! n1 outer diameter 50w
The paint is applied to the jagged peripheral edge of the transfer disk 10 of the un, and the transfer disk 10 is rotated along the center line of the tread strip 1 using the small groove 3 as a guide groove, and the paint is transferred to the bottom surface of the small groove 3. This creates a highly visible color line.

Therefore, the center line of width is always drawn. Note that the color rubber paint that stands out is not particularly limited as long as it is a color that stands out, such as white or yellow, which is different from the color of the treaded rubber, but the paint used in this example is a white rubber paint, and is a natural rubber 7. A composition obtained by kneading parts by weight of SBR3O, 6 parts by weight of titanium oxide, 2 parts by weight of sulfur, and 3 parts by weight of zinc white in a rubber mixer was dissolved in 50 parts by weight of volatile oil. Rubber paints are generally made from natural rubber, SBRl or BR.
20 to 1 (4) parts by weight of a coloring pigment is used per 10 parts by weight of one or two selected rubbers, and if necessary, zinc white, sulfur, a vulcanization accelerator and a softening agent are used. A blended mixture dissolved in an organic solvent such as volatile oil or triol is used. The steps other than the step of forming the color center line 4 on the tread strip 1 described above are based on conventional molding of various types of tires.

Therefore, based on an example of the outline of the green tire forming process,
Reference will be made to the green tire forming of this invention.

To mold a green tire, first, a rubberized tire cord is wrapped around the drum of a molding machine to form a carcass ply, and bead rings fitted with bead cores 14 are accurately pressed against both sides of the molding drum. A bead core 14 is precisely placed on the carcass, and a carcass ply is rolled up around it to form a carcass 12 in the conventional manner. A beam (a bundle of relatively parallel light rays emitted from one light source) is directed onto the carcass 12 rotating on the drum of this molding machine.
Specify the center position of the carcass 12 by irradiating the tread strip 1L with the center position of the width L of the crown part 2 of the tread strip 1L. The tread strip 1 is superimposed on the carcass 12 while aligning the color center line 4 filled with colored rubber paint in the small groove 3 provided in the carcass 12, and the tread rubber part 1
1 and stitchers (ST
(ITCHER) While moving the roll, the tread comb part 11 is pressed against the carcass 12, and the air existing on the adhesive surface is discharged, thereby strengthening the adhesive force between the two.

In this case, since the color center line 4 is drawn in the small groove 3, there is no risk of it being rubbed or erased by the stitcher roll.

Next, the sidewall rubber 13 is continuous to the tread rubber portion 11 and polymerized on the carcass 12 to form the green tire GT shown in FIG.

Next, the color center line 4 of the raw tire GT removed from the drum of the molding machine is referenced to the center dividing plane of the vulcanization mold, which is divided into upper and lower parts, that is, the center position, which is the vertically symmetrical plane of the mold. The materials are then placed in a vulcanization mold in an accurate relative position, and the mold is closed to perform vulcanization molding.

In this vulcanization molding, if the center position of the upper and lower symmetry planes of the mold matches the color center line 4, the center of gravity of the tire will be on the circumferential center plane of the tire, resulting in a tire that is well-balanced in terms of mass. is obtained. Therefore, after vulcanization molding, check the color center line 4 against the parting line 15 of the vulcanized tire VT formed on the dividing surface of the mold, and if it is correctly loaded into the vulcanization mold, the color center Line 4 is parting line 15
The color center line state is lost as the color overlaps with the color center line and almost disappears.

Therefore, if the groove of the trend pattern or the color center line that partially remains when it protrudes is on the tire offset from the parting line 15, this is an indication that the tire has poor uniformity. By measuring the distance of deviation, the degree of uniformity can be estimated.

Therefore, if the range of deviation of the color center line from the parting line is determined by comparing it with the degree of uniformity that does not cause any practical problems, uniformity can be determined without expensive inspection equipment and trouble.

In addition, in the case of a mold in which the upper and lower dividing surfaces of the vulcanization mold are in asymmetrical positions due to trend patterns, etc., the upper and lower dividing surfaces of the vulcanization mold are placed on the inner circumferential surface of the vulcanization mold, which corresponds to the center position of the upper and lower sides. A line is engraved on the inner surface of the mold at the center position, which is the symmetrical plane between the top and bottom of the vulcanization mold.This line is used as the reference line, and the distance between this reference line and the dividing surface of the mold is measured. Then, the color center line 4 of the green tire GT is placed relative to the reference line of the vulcanization mold and loaded, and when vulcanization is performed, the distance between the color center line 4 and the parting line is checked. This makes it possible to determine the uniformity of the tire.

In addition, a tire formed using a conventional green tire without a color center line and a tire formed using a green tire with a color center line of the present invention were each inspected using a 100 pot uniformity inspection machine. As a result, the rejection rate was 1% for the tires of the present invention, compared to 5% for tires using the conventional method.

Additionally, there is a correlation between the deviation of the color center line of a vulcanized tire from the parting line and the uniformity measured by a uniformity inspection machine, with a correlation coefficient of 0.90. Ta.

As mentioned above, in the method for manufacturing a pneumatic retirement according to the present invention, an easily distinguishable color center line drawn in a small groove is set at the center position of the tread strip, so that the carcass is easily formed on the rotating drum of the molding machine. In addition to being extremely easy to overlay accurately at the center of the width, it is also easy to accurately load the green tire into the mold, so tires with excellent uniformity can be obtained with a high probability.

In addition, the uniformity of the tire can be easily determined based on the state of loss of the color center line state and the distance from the color center line, so it is possible to determine whether the tire is good or bad just by looking at the state taken out of the vulcanization mold. Therefore, there is no need for an expensive uniformity inspection machine and inspection procedures. When measuring with an inspection machine, preliminary work such as assembling the rim of the tire to be inspected is required, and the inspection requires a considerable amount of effort. Moreover, it not only contributes to improving production efficiency, but also significantly reduces the defective rate, making it easier to produce uniform pneumatic retirements suitable for high-speed running, and greatly contributing to lowering production costs.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view of a main part showing the process of forming a color center line of a tread strip; FIG. 2 is a partial perspective view of a main part showing an axial cross section showing an example of a green tire of the present invention; FIG. 3 is a front view schematically showing the parting line immediately after being taken out from the vulcanization mold. 1...Tread strip, 2...Crown part, 3
...Small groove, 4...Color center line, GT...Raw tire, 12...Carcass, 15...Parting line.

Claims (1)

[Claims] 1. Extrude a tread strip with a small groove provided at the center of the width of the crown part of the tread strip, fill the small groove with rubber paint of a conspicuous color different from the color of the tread rubber to give a color center line, and place it on a tire molding machine. Align the color center line of the tread with the center position of the width of the carcass formed, polymerize on the carcass to form a green tire, and align the color center line of the tread of this green tire with The parting line and color center line formed by the dividing surface of the vulcanization mold are placed relative to the center position of the upper and lower symmetrical surfaces of the vulcanization mold, loaded into the vulcanization mold, and vulcanized. A method for manufacturing a pneumatic tire, characterized by contrasting the two.